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F30 / F31 / F32 / F33 / F36 (2012 - current)
The sixth generation 3 series, chassis code F30. 2013 model year 328i and 335i sedans now in production. Read the F30 frequently asked question thread for all your basic question and dive into all the details in the ultimate F30 information thread.

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  #26  
Old 04-30-2013, 11:23 AM
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BmwFlooner BmwFlooner is offline
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Quote:
Originally Posted by SergioK View Post
The clutch pedal and clutch disc are controlled via a hydraulic system. It's a closed system thus speed of clutch engagement can vary depending on how fast you depress the clutch pedal. The CDV aims to slow down the actual engagement of the clutch if you simply 'pop' your foot off the clutch pedal.
That was my understanding, and that it's something that doesn't interfere with normal shifting.
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  #27  
Old 04-30-2013, 12:41 PM
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Zeichen311 Zeichen311 is online now
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Quote:
Originally Posted by SergioK View Post
The clutch pedal and pressure plate are controlled via a hydraulic system. ... The CDV aims to slow down the actual engagement of the clutch if you simply 'pop' your foot off the clutch pedal.
Fixed. The friction disc is splined to the transmission input shaft; the pedal controls the pressure plate bolted to the engine flywheel.

Quote:
Originally Posted by BmwFlooner View Post
That was my understanding, and that it's something that doesn't interfere with normal shifting.
Partially incorrect. The design intent is to protect the driveline from "dumping" or "popping" the clutch as described. However it most certainly does interfere with normal shifting. The restriction is asymmetric--the restriction is greater when engaging than disengaging the clutch--and the orifice in the valve is so small (~10% of the unrestricted cross-sectional area) that the system is not operating in the linear range. That is, the movement rate of the clutch linkage is not in constant proportion to the movement rate of your foot; it varies with the speed of release.

The net result is that the CDV makes it exceedingly difficult to achieve consistent, smooth clutch engagement, because the precision with which the clutch fork responds to pedal travel is significantly reduced. The non-linearity makes it hard to compensate for the minute added delay because the delay is not constant.

(The above applies to the E9x valving. The F30 is no doubt similar if it has a CDV, or "lock valve" as it is officially called.)
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Last edited by Zeichen311; 04-30-2013 at 01:15 PM.
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  #28  
Old 04-30-2013, 12:56 PM
Jamesonsviggen Jamesonsviggen is offline
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Quote:
Originally Posted by Zeichen311 View Post
Fixed. The friction disc is splined to the transmission input shaft; the pedal controls the pressure plate bolted to the engine flywheel.

Partially incorrect. The design intent is to protect the driveline from "dumping" or "popping" the clutch as described. However it most certainly does interfere with normal shifting. The restriction is asymmetric--the restriction is greater when engaging than disengaging the clutch--and the orifice in the valve is so small (~10% of the unrestricted cross-sectional area) that the system is not operating in the linear range. That is, the movement rate of the clutch linkage is not in constant proportion to the movement rate of your foot; it varies with the speed of release.

The net result it that the CDV makes it exceedingly difficult to achieve consistent, smooth clutch engagement, because the precision with which the clutch fork responds to pedal travel is significantly reduced. The nonlinearity makes it hard to compensate for the minute added delay because the delay is not constant.

(The above applies to the E9x valving. The F30 is no doubt similar if it has a CDV, or "lock valve" as it s officially called.)
Thanks, saved me the typing lol.
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  #29  
Old 04-30-2013, 01:20 PM
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BmwFlooner BmwFlooner is offline
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Quote:
Originally Posted by Zeichen311 View Post
Fixed. The friction disc is splined to the transmission input shaft; the pedal controls the pressure plate bolted to the engine flywheel.

Partially incorrect. The design intent is to protect the driveline from "dumping" or "popping" the clutch as described. However it most certainly does interfere with normal shifting. The restriction is asymmetric--the restriction is greater when engaging than disengaging the clutch--and the orifice in the valve is so small (~10% of the unrestricted cross-sectional area) that the system is not operating in the linear range. That is, the movement rate of the clutch linkage is not in constant proportion to the movement rate of your foot; it varies with the speed of release.

The net result is that the CDV makes it exceedingly difficult to achieve consistent, smooth clutch engagement, because the precision with which the clutch fork responds to pedal travel is significantly reduced. The non-linearity makes it hard to compensate for the minute added delay because the delay is not constant.

(The above applies to the E9x valving. The F30 is no doubt similar if it has a CDV, or "lock valve" as it is officially called.)
Thanks for the writeup

That sounds pretty undesirable. So the 99% of time you're shifting suffers to protect you against the 1% of the time you bork a shift?

I assume removing it has implications for warranty claims against the clutch.
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